collect_by_key

Map[P, Array[Y]] collect_by_key(Array[Pair[P, Y]])

Given an Array of Pairs, creates a Map in which the right elements of the Pairs are grouped by the left elements. In other words, the input Array may have multiple Pairs with the same key. Rather than causing an error (as would happen with as_map), all the values with the same key are grouped together into an Array.

The order of the keys in the output Map is the same as the order of their first occurrence in the input Array. The order of the elements in the Map values is the same as their order of occurrence in the input Array.

Parameters

1. Array[Pair[P, Y]]: Array of Pairs to group.

Returns: Map of keys to Arrays of values.

Example: test_collect_by_key.wdl

version 1.3

workflow test_collect_by_key {
  input {
    Array[Pair[String, Int]] x = [("a", 1), ("b", 2), ("a", 3)]
    Array[Pair[String, Pair[File, File]]] y = [
      ("a", ("data/questions.txt", "data/answers.txt")),
      ("b", ("data/request.txt", "data/response.txt")),
      ("a", ("data/wizard.txt", "data/spell.txt"))
    ]
    Map[String, Array[Int]] expected1 = {"a": [1, 3], "b": [2]}
    Map[String, Array[Pair[File, File]]] expected2 = {
      "a": [("data/questions.txt", "data/answers.txt"), ("data/wizard.txt", "data/spell.txt")],
      "b": [("data/request.txt", "data/response.txt")]
    }
  }

  output {
    Boolean is_true1 = collect_by_key(x) == expected1
    Boolean is_true2 = collect_by_key(y) == expected2
  }
}

{}

{
  "test_collect_by_key.is_true1": true,
  "test_collect_by_key.is_true2": true
}